Roland Piquepaille writes "It's widely accepted today that nanotechnology will soon be able to deliver medicine inside the human body or to do research on cells. But to achieve this goal, you need nano-cargos moving through liquid environments, such as blood. And this is a very difficult challenge because the nano-swimmers have to struggle with blood's viscosity, which has very large effect in a nanoscale environment. But now, two Iranian researchers have found a simple and elegant solution to this problem, based on the principle of non-reciprocal motion and described in "Teaching Nanotech to Swim" by Technology Review. Their nano-swimmer consists of three aligned spheres connected by two rigid rods which can contract and expand. The nano-cargo then advances in the blood like an earthworm inside the soil. Even if these nano-swimmers look promising, nobody knows when they will be able to deliver drugs in our bodies. Read this summary for more details and references. You'll also find an illustration showing how the nano-swimmer moves."